base.bbclass: Fix incorrect setting of multilib PREFERRED_PROVIDER_virtual_pkg
PREFERRED_PROVIDER_virtual_pkg has been incorrectly set with more
than one multilib prefixes. For example, if we have two alternative
multilibs lib64 and lib32, PREFERRED_PROVIDER_virtual_pkg will be
set to lib32-lib64-pkg or lib64-lib32-pkg, depending on which
multilib shows up first in the list.
Signed-off-by: Lei Liu <lei.liu2@windriver.com> Signed-off-by: Robert Yang <liezhi.yang@windriver.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
